Nitrosodisulfonate latensifier



Unimd States Patent NITROSODISULFONA'IE LATENSIFIER Gershon M. Goldberg, Arlington, and James E. Lu Valle, Lexington, Mass., assignors to Technical Operations, Incorporated, Burlington, Mass., a corporation of Delaware No Drawing. Filed Dec. 23, 1957, Ser. No. 704,292

4 Claims. (Cl. 96-65) The fieldvof this invention is the intensification of the 2,938,793 Patented May 31, 1960 ice fore development with a solution containing nitrodisul fonate ions of the following formula:

Examples Type of Film Speed Percent Speed Increase Conditions Latensllatent photographic image in exposed silver halide emulsion material, and more particularly the intensification of such images after exposure and before development.

The principal objects of this invention are to provide an improved latensifying method which is more closely reproducible than previous methods, which produces a lower fog level and which efiectively latensifies X-ray film to reduce the necessary exposure time of patients and technicians.

The concept latensification refers to the treatment of an exposed silver halide emulsion film after exposure but before development, to intensify the latent image and thereby to reduce the exposure time necessary to obtain a required picture quality. Latensification with previously known agents such as hydrogen peroxide, sodium perborate or potassium metabisulfite has been carried out by bathing the film strips in solutions of these agents, drying and then developing. The drying period was an essential part of the procedure. However with latensification according to this invention drying is not required. Handling is thereby minimized and undesirable effects such as streaking of the film due to uneven drying are avoided.

In a brief summary of this invention, improved latensification is obtained in the process of developing an exposed photographic silver halide emulsion by the step Which comprises treating the film after exposure and be- Plus X Plus X Plus X Plus X Trl X Super XX X-ray-Type F X-ray-Type M.

pH 10.5, 0.0125 M sol'n, 2 minutes prebath; 4 min. development in D 19.

pH 10.5, 0.00125 M soln, 16 minutes prebath; 4 min. development in D 19.

pH 10.5, 0.0125 M sol'n, 2 min.

prebath; 16 min. development in Microdol.

pH 10.5, 00125 M soln, 2 min.

prebath; 4 min. development in D- pH 10.5, 0.0125 M sol'n, 2 min.

prebath; 4 min. development in DK 50.

pH 10.5, 0.0125 M soln, 16 min.

prebath; 4 min. development in D 19.

pH 10.5, 0.0125 M soln, 4 min.

prebath; 4 min. development in D 19.

pH 10.5, 0.0125 M soln, 2 min.

prebath; 8 min. development in Kodak X-ray developer.

pH 10.5, 0.0125 M sol'n, 12 min.

prebath; 8 min. development Kodak 'X-ray developer.

All of the film and developers in the above examples are products of the Eastman Kodak Company. Developers D-19, D-76 and DK-SO are hydroquinoneElon (p-methyl aminophenol sulfate) combinations whose compositions are disclosed in section six of the Photo-Lab- Index by Henry M. Lester, published by Morgan and Lester, 101 Park Avenue, New York 17, New York. Kodak X-ray developer is also a hydroquinone-Elon combination while Microdol is an Elon formulation. The film types illustrated are high speed negative gelatinsilver halide emulsions having the properties set forth in Kodak Films, 7th ed. (1956).

The data included in the above examples were obtained by exposing strips of the test film through a standard step wedge followed by development in a standard processing unit. The density of the resulting wedges was measured and H and D curves plotted. The speed was taken as the antilog (3-log E) at D=0.2 above (fog+base). Cations suitable for use with the nitrosodisulfonate anion include sodium, potassium, lithium and ammonium. The prebath treatment refers to latensification by immersion of the exposed film in an agitated bath of nitrosodisulfonate ion solution in water at the indicated pH and concentration. These tests were conducted at 68 F. The latensified test films were washed for one minute in water before development.

These data show that nitrosodisulfonate radical ions 3 V in solution are capable of intensifying the latent image and increasing the speed by an amount varying up to 150% depending upon the type of film used, the developer. and the length of treatment. The latensifying treat- 7 meat of vthis invention raises the fog level of the film onlyv about 10-1 5% which is considerably :less than the increase caused by previous 'methods. I This treatment is alsocsuperior because the result is more closely reproducible. Drying is not required after treatment there 'by eliminating streaking caused by'uneven drying and requiringless handling 'of the film.- -A'ccording to the present process the exposed film strip is treated with a nitrosodisulfonate ion'solution, then washed in water for one minute and can then be developed while still-wet. The water wash after latensific'ation is'not essential but is recommended because the nitrosodisulfonate radical will oxidize. developersmolecules. While the amount of latensifier remaining on the treated film isismall, this oxidation would; decrea e the Reusable. life of developer solutions. Where fresh developer is used, the result on the film without washing is substantially the same as processing which utilizes the water wash. 1 p 7 Solutions containing nitrosodisulfonate radical ions are net stable at iow'pni Therefore best results are obtained above pH 8 withthe optimum pH being between about 10 and 11.- At highenpHs an undesirable increase in fog level accompanies the latensification. The desired pH is. conveniently obtained with -a carbonate-bicarbonate bufier system. Suitable concentration forv the nitrosodisulfonate ions can vary from 0.001 molar to about 0.0125

molar. While higher concentrations maybe employed,

no appreciable gain results. The latensification obtained speed film types as shown .in theexamples above. The contrastis' not visibly affected by the treatment.

It is an important aspect-of this invention that treatsource of increasing concern.

ment with a nitrosodisulfonate ion solution latensifies X- h ray film. With this treatment-it is possible to reduce the exposure time of patients and X-ray technicians to radia- W 4 tion while still. obtaining the same picture. This is very desirable since excess exposure is dangerous and is a Potassium and sodium nitrosodisulfonate can be prepared as set forth in Murib and Ritter, I. Am. Chem. Soc. 74, 3394 (1952), and Harvey and Hollingshead, Chemistry and Industry 244 (1953). Other salts can be prepared by varying the salting out procedure described in these references. according to well. known techniques. Potassium nitrosodisulfonate is commercially available from the AldrichChemical Co. of Milwaukee, Wisconsin.

We claim:

1. m me process of developing an exposed photographic silver halide emulsion, the step which comprises latensifying the film after exposure and before development with a solution containing a member selected from the group consisting of alkali metal and ammonium nitrosodisulfonates.

2. The step according to claim 1 wherein the solutionis a water solution having 'a pH between about 10 and 11. I Y

3. The process of forming a photographic image which v includes exposing a photosensitive silver halide emulsion,

thegroup consisting of alkali metals and ammonium and developing the latensified film without intermediate drying.

- and before development with a solution containing a according to this invention is most effective with higher W member selected from the group consisting of alkali 1 metal and ammonium nitrosodisulfonates.

Schestakofi Mar. 27, 1928 Weyerts et al Mar. 9, 1948 mlwum 

1. IN THE PROCESS OF DEVELOPING AN EXPOSED PHOTOGRAPHIC SILVER HALIDE EMULSION, THE STEP WHICH COMPRISES LATENSIFYING THE FILM AFTER EXPOSURE AND BEFORE DEVELOPMENT WITH A SOLUTION CONTAINING A MEMBER SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL AND AMMONIUM NITROSODIUSLFONATES. 